JPH07254153A - Method for outputting information in information recording medium - Google Patents

Abstract

PURPOSE:To read out high density recorded information and to display it without using a light source by using a compd. producing a significant difference in the intensity of fluorescence or electroluminescence at the time of crystalline- amorphous transition in an information recording medium. CONSTITUTION:Metal Cr is vapor-deposited on a glass sheet to form a photo- thermal conversion layer. A compd. considerably reducing the intensity of fluorescence by transition from a crystalline state to an amorphous state is put on a glass substrate and melted by heating. The glass sheet is brought into contact with the resultant melt with the conversion layer downward so as to uniformly hold the melt. The compd. is then allowed to form a recording layer of an amorphous solid by cooling the glass substrate to obtain an optical recording medium. This recording medium is irradiated with a specified laser beam spot to record information. The recorded part emits fluorescence and enables readout. When the recorded part is irradiated with another specified laser beam spot, the irradiated part loses its fluorescence and the record is erased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information output method for an information recording medium applied to an optical disc, a display recording element and the like.

[0002]

2. Description of the Related Art In recent years, rewritable high density recording media have been actively studied. Among them, it is known that a recording medium utilizing a physical crystal-amorphous transition has a higher repeating durability than a recording medium involving a chemical reaction. However, in a recording medium utilizing the crystal-amorphous transition, it is general to read the recorded information by detecting the difference in reflectance between the conventional crystal and the amorphous, and read with sufficient sensitivity. However, the recording area cannot be made too small to carry out, and there is a limit to the increase in density. Further, in detecting the reflected light from the recording medium, it is necessary to strictly control the position of the detecting means, which causes a problem that the system is likely to be upsized.

Further, the recording materials used for such recording media have hitherto been mainly limited to inorganic substances. This is because few low molecular weight organic substances except polymers maintain a stable amorphous state at room temperature or higher, and on the other hand, polymers can maintain a stable amorphous state, but crystallization does not easily occur. This is because it is difficult to use as a recording medium. However, in a recording medium that utilizes the crystal-amorphous transition of an inorganic substance, the transition temperature is high, so it is necessary to use a substrate having heat resistance. Further, among the inorganic substances, metals and semiconductors have large thermal conductivity and thus require a large amount of energy for recording and erasing, and it is difficult to increase the density because the recording spot becomes large.

On the other hand, in recent years, rewritable display recording media using organic substances have been actively studied. For example,
A combination of a leuco dye and a color-developing / decoloring material to reversibly cause color development and color erasing (JP-A-4-50290), and changes transparency depending on coagulation conditions of organic crystal particles in a matrix polymer. What is allowed (Japanese Patent Laid-Open No. 54-1)
No. 19377), a method of changing the transparency by utilizing the thermal behavior of the molecular arrangement of a liquid crystal polymer (JP-A-4-13).
No. 0412), which causes a change in a colored state by utilizing a crystal-amorphous transition (Mol. Cryst. Li).
quid Crystal. , 1993, 235, p. 14
7) etc. are proposed. However, these display recording media have a problem that a separate light source is required for reading information.

[0005]

As described above, the crystal-
The conventional rewritable recording medium utilizing the amorphous transition has a problem that it is difficult to downsize the system and the recording density is low. Further, there is a problem that a conventional display recording medium using an organic substance requires a separate light source.

An object of the present invention is to output information from an information recording medium utilizing a crystal-amorphous transition, which is advantageous for downsizing of a system and which can be applied to reversible information recording with high sensitivity and high density. To provide a method. Another object of the present invention is to provide an information output method for an information recording medium utilizing a crystal-amorphous transition, which does not require a light source for outputting recorded information.

[0007]

The information output method for an information recording medium according to the present invention is a method for recording information by utilizing the crystal-amorphous transition of a recording material. It is characterized by detecting the sense intensity and outputting the recorded information.

The inventors of the present invention have long been conducting research on an electroluminescence (EL) device using a vapor deposition film of an organic material. An EL element requires a thin film with a thickness of about several tens of nm to reduce the applied voltage, and withstands the vapor deposition process of the upper electrode, does not cause an electrical short circuit, and produces an element with good operation stability. Therefore, it is necessary to use an amorphous organic thin film. From these perspectives,
The present inventors have been able to clarify a specific molecular structure of a dye molecule that has a high glass transition temperature (Tg) and can maintain a stable amorphous state.

In addition, most of the dye molecules having a high Tg as described above are largely different in crystalline or amorphous fluorescence intensity or EL intensity. Based on such knowledge, the present inventors have completed the present invention by using a dye molecule having a high Tg as a recording material. Here, the results of studies on organic dyes whose fluorescence intensity changes due to the crystal-amorphous transition will be described more specifically. In the course of these studies, a crystal powder obtained by purifying a commercially available product or a dye molecule obtained by synthesis by recrystallization or sublimation was used. Further, these crystals were melted and then rapidly cooled or vapor-deposited on a non-fluorescent glass substrate to make them amorphous. Whether crystalline or amorphous was examined by X-ray diffraction. The fluorescence intensity was visually evaluated using a UV lamp as an excitation light source. As a result, the following A-1 to A-
It has been found that the dye molecule shown by 8 has a particularly large decrease in fluorescence intensity when it transitions from crystalline to amorphous.

[0010]

[Chemical 1]

[0011]

[Chemical 2]

[0012]

[Chemical 3]

The organic dye molecule generally has the highest fluorescence intensity when it has a planar structure, and has the weakest fluorescence intensity when it has a non-planar structure. Therefore, in the present invention, it is preferable that the recording material is a molecule in which a crystal structure having a small degree of freedom is likely to have a planar structure and an amorphous state having a large degree of freedom is unlikely to have a planar structure. However, for complex dye molecules, the crystal structure or amorphous structure changes due to slight differences in the molecular structure such as substituents, so predict the crystal structure or amorphous structure under given conditions. Is extremely difficult. For this reason, it is effective to actually manufacture crystals and amorphous materials and evaluate their fluorescence intensities as described above. Regarding organic dye molecules, it is known that the higher the fluorescence intensity is, the higher the EL intensity is. Therefore, even when the EL intensity is detected, the dye molecules whose fluorescence intensity greatly changes between crystalline and amorphous in the element. Is still suitable.

In the present invention, if the crystal-amorphous transition can be utilized and the difference in fluorescence intensity or EL intensity between the crystal and the amorphous is sufficient, an inorganic substance is used as the recording material. You can also However, as described above, since an inorganic substance generally has a high transition temperature at which a crystal-amorphous transition occurs and has a high thermal conductivity, it is preferable to use an organic dye in the present invention. That is, in the present invention, an optical recording medium or display recording medium having a thin film of organic dye molecules is usually produced. As a method for producing a thin film of organic dye molecules, various methods such as casting method, vapor deposition method, LB method, water surface development method, and electrolysis method can be applied. Of these, the casting method is the simplest and the vapor deposition method is excellent for producing a multilayer structure film. A thin film in which an organic dye is dispersed in a suitable binder can also be used.

The principle of recording / erasing in the present invention will be described below. In the present invention, for example, a thin film made of an amorphous organic dye molecule is formed. In this state, the fluorescence intensity and EL intensity are almost zero or extremely small. This is the initial state in which this state is not recorded. Next, a part of the thin film made of an amorphous organic dye molecule is heated to transform the amorphous into a crystal. In the crystallized portion, the fluorescence intensity and EL intensity are significantly increased. Recording is performed by this operation. Furthermore, after the crystal is heated and melted, it is rapidly cooled to return to an amorphous state. This operation erases. However, the present invention is not limited to a rewritable information recording medium capable of erasing recorded information based on a reversible reversible crystal-amorphous transition, and is not limited to a DRAW (Direct).
It can also be applied to a Read After Write) type information recording medium and the like.

The principle of recording / erasing described above will be described with reference to FIG. FIG. 1 is a diagram showing the temperature dependence of the specific volume of a recording material. When a part of the amorphous recording material is heated to the crystallization temperature Tc at room temperature below the glass transition point Tg, it is transformed into crystals via the supercooled liquid and recording is performed. When this recording material is heated to the melting point Tm and the melted liquid is rapidly cooled, the original amorphous state is restored and erasing is performed.

On the contrary, contrary to the above, the initial state is crystalline and the fluorescence intensity and EL intensity are extremely high. A part of the crystalline substance is heated to melt the crystalline substance, and then the crystalline substance is rapidly cooled to be amorphous. Alternatively, recording can be performed by a method of significantly reducing the fluorescence intensity and EL intensity of that portion. In this case, erasing is performed by heating the amorphous material to crystallize it. However, in the present invention, when recording is performed by utilizing the transition from amorphous to crystalline, since this process is a heat generation process, the input amount of thermal energy can be reduced, and high sensitivity and high speed recording can be performed. It will be possible. In addition, in the recording material as described above, if the amorphous material is unstable, the crystallization proceeds to the whole and the recorded information is erased by installation at room temperature or slight heating. The crystallization temperature Tc at which the amorphous crystallization progresses is present in the temperature range between the glass transition point Tg and the melting point Tm, although it varies depending on the heating temperature. Therefore, the glass transition of the recording material used in the present invention. The point Tg needs to be at least room temperature (25 ° C.) or higher, and more preferably 50 ° C. or higher. On the other hand, if the amorphous material is too stable, a large amount of heat energy is required for crystallization, which makes it difficult to perform recording and erasing at high speed. Therefore, the glass transition temperature Tg of the recording material is 150 ° C. or less. It is preferable.

Next, specific means for recording and erasing in the present invention will be described. In the present invention, the crystal-
As mentioned above, thermal energy is used to cause the transition between amorphous materials. As a means of applying heat energy,
Laser light or a thermal head can be used. Laser light that can reduce the spot diameter is advantageous for high-density recording. In order to efficiently absorb the laser light into the organic dye molecule, it is generally preferable to provide a light absorption layer, a photothermal conversion layer, etc., which absorbs the laser wavelength. Further, although the thermal head does not have a high resolution, it is convenient for heating a large area and for heating a transparent substance, and is suitable for a display recording medium. These heating methods are generally used in recording operations. On the other hand, for the erasing operation, a hot plate pressing method or a rolling method capable of heating the recording medium at one time is preferable. Further, natural heat may be radiated to cool the heated recording medium, but a cold plate pressing method, a roll method, or a method of rapidly cooling with a cold air flow is preferable.

In the present invention, when the fluorescence intensity is detected and the information recorded on the information recording medium is output, the wavelength of the excitation light and that of the fluorescence are different, so that the fluorescence intensity measurement sensitivity (recording read sensitivity) is high. can do. Moreover, since the fluorescence is emitted in all directions even if the light emitting area is small, the recording area can be made extremely small, which is suitable for high density recording. For example, recently, fluorescence emission from one molecule has also been measured, and in principle, ultra-high density recording up to near the molecular size is possible. Further, in detecting fluorescence, strict position control of the detection means is not required, and the system can be downsized. In addition, when the EL intensity is detected and information is output, self-light emission is exhibited simply by applying a predetermined electric field to the information recording medium, so that a separate light source is not required. Further, in any case, unlike the method of detecting the difference in reflectance or absorptance, it is not necessary to strictly control the film thickness, which is advantageous in the manufacturing process.

[0020]

EXAMPLES Examples of the present invention will be described below. Example 1 (High Density Optical Recording Medium) Chromium metal was vapor-deposited on a glass plate having a thickness of about 0.1 mm to form a photothermal conversion layer. On the other hand, the optically polished thickness 1.
The compound represented by Structural Formula (A-1) was placed on a 2 mm glass substrate and heated and melted. The glass plate was brought into contact with the melt with the light-heat conversion layer side facing down, and the melt was uniformly spread over the entire surface and sandwiched. Next, this glass substrate was pressed against an aluminum plate cooled with water to cool the melt, thereby forming a recording layer made of an amorphous solid of the compound (A-1). As described above, an optical recording medium having a structure of glass substrate / recording layer / photothermal conversion layer / glass plate was produced.

While rotating this optical recording medium at 900 RPM, a laser beam having a wavelength of 780 nm was irradiated from a semiconductor laser under the conditions of a spot diameter of 1 μm and an irradiation intensity of 1 mW. After that, as a result of observing the optical recording medium with a fluorescence microscope, a width of about 1 μm that emits strong fluorescence to the laser beam irradiation part
The line of m was recognized with a clear contrast. Also,
As a result of observing this optical recording medium with a polarization microscope, it was also found that crystallization occurred linearly. From these results, it was confirmed that recording was made.

Next, while rotating the optical recording medium after recording, a laser beam having a wavelength of 780 nm was irradiated from a semiconductor laser under the conditions of a spot diameter of 2 μm and an irradiation intensity of 8 mW. After that, when the optical recording medium was observed with a fluorescence microscope, the recording was erased in the region scanned with the laser beam.

Example 2 (High Density Optical Recording Medium) Example 1 except that as the recording layer, the compound represented by the structural formula (A-2) was used in place of the compound represented by the structural formula (A-1). An optical recording medium having a structure of glass substrate \ recording layer \ photothermal conversion layer \ glass plate was prepared in the same manner as in.

While rotating this optical recording medium at 900 RPM, a laser beam having a wavelength of 780 nm was irradiated from a semiconductor laser under the conditions of a spot diameter of 1 μm and an irradiation intensity of 1 mW. After that, as a result of observing the optical recording medium with a fluorescence microscope, a width of about 1 μm that emits strong fluorescence to the laser beam irradiation part
The line of m was recognized with a clear contrast. Also,
As a result of observing this optical recording medium with a polarization microscope, it was also found that crystallization occurred linearly. From these results, it was confirmed that recording was made.

Next, while rotating the optical recording medium after recording, a laser beam having a wavelength of 780 nm was irradiated from a semiconductor laser under the conditions of a spot diameter of 2 μm and an irradiation intensity of 8 mW. After that, when the optical recording medium was observed with a fluorescence microscope, the recording was erased in the region scanned with the laser beam.

Example 3 (High Density Optical Recording Medium) Chromium metal was vapor-deposited on a glass substrate having a thickness of 1.2 mm to form a photothermal conversion layer. The weight ratio of the compound represented by the structural formula (A-3) to polymethylmethacrylate is 1:
A THF solution containing 1 ratio was prepared. Then, the THF solution was applied onto the photothermal conversion layer and dried on a hot plate at 60 ° C. to form a recording layer. As described above, an optical recording medium composed of the glass substrate / light-heat conversion layer / recording layer was produced.

While rotating this optical recording medium at 900 RPM, a laser beam having a wavelength of 780 nm was irradiated from a semiconductor laser under the conditions of a spot diameter of 1 μm and an irradiation intensity of 1 mW. After that, as a result of observing the optical recording medium with a fluorescence microscope, a width of about 1 μm that emits strong fluorescence to the laser beam irradiation part
The line of m was recognized with a clear contrast. Also,
As a result of observing this optical recording medium with a polarization microscope, it was also found that crystallization occurred linearly. From these results, it was confirmed that recording was made.

Next, while rotating the optical recording medium after recording, a laser beam having a wavelength of 780 nm was irradiated from a semiconductor laser under the conditions of a spot diameter of 2 μm and an irradiation intensity of 8 mW. After that, when the optical recording medium was observed with a fluorescence microscope, the recording was erased in the region scanned with the laser beam.

Example 4 (Display recording medium) Al was vapor-deposited on a glass substrate of 50 × 50 × 1 mm, and an oxadiazole derivative (electron transport layer) represented by the structural formula (1) was vapor-deposited to a thickness of 50 nm. Then, the oxadiazole derivative (light-emitting layer) represented by the structural formula (A-2) is added to 50 nm.
And a carbazole derivative (electron transport layer) represented by the structural formula (2) was deposited to a thickness of 50 nm. Finally, an ITO transparent electrode was formed by a sputtering method to prepare a display recording medium.

[0030]

[Chemical 4]

Next, using a thermal simulator (manufactured by Toshiba Corp.), the display recording medium was heated so as to print a "T" character, and the oxadiazole derivative of (A-2) as the light emitting layer was heated. A portion was crystallized. When this display recording medium was driven with a direct current voltage of 10 V, the "T" letter that strongly emitted light appeared clearly. Next, this display recording medium was pressed on a hot plate for 2 seconds and then rapidly cooled to partially amorphize the oxadiazole derivative. When this display recording medium was driven with a DC voltage of 10 V, the "T" character was completely erased and no pattern was recognized.

Example 5 (Display Recording Medium) Example 5 (Display Recording Medium), except that the compound represented by the structural formula (A-1) was used in place of the compound represented by the structural formula (A-2) in the light emitting layer. A display recording medium was prepared in the same manner as in 4.

Next, using a thermal simulator (manufactured by Toshiba Corporation), the display recording medium was heated so as to print a "T" character, and the oxadiazole derivative of (A-1) as the light emitting layer was heated. A portion was crystallized. This display element 1
When it was driven with a direct current voltage of 0 V, a strongly emitting "T" was clearly shown. Next, this display recording medium was pressed on a hot plate for 2 seconds and then rapidly cooled to partially amorphize the oxadiazole derivative. When this display recording medium was driven with a DC voltage of 10 V, the "T" character was completely erased and no pattern was recognized.

Example 6 (Display recording medium) Al was vapor-deposited on a glass substrate of 50 × 50 × 1 mm, and an oxadiazole derivative (electron transport layer) represented by the structural formula (1) was vapor-deposited to a thickness of 20 nm. Then, the oxadiazole derivative (light-emitting layer) represented by the structural formula (A-2) is added to 20 nm.
And a carbazole derivative (electron transport layer) represented by the structural formula (2) was deposited to a thickness of 50 nm. Copper phthalocyanine was vapor-deposited thereon to a thickness of 30 nm. Finally, an ITO transparent electrode was formed by a sputtering method to prepare a display recording medium.

A laser beam having a wavelength of 630 nm from a semiconductor laser was spotted on this display recording medium at a spot diameter of 1 μm.
Irradiation was performed under the condition of irradiation intensity of 1 mW. When this display recording medium was driven with a direct current voltage of 10 V, a line having a width of about 1 μm showing strong light emission was observed in the laser beam irradiation portion with clear contrast.

Next, the display recording medium after recording was irradiated with a laser beam having a wavelength of 630 nm from a semiconductor laser under the conditions of a spot diameter of 2 μm and an irradiation intensity of 8 mW. When this display recording medium was driven with a DC voltage of 10 V, it was found that the EL intensity was reduced in the region scanned with the laser beam, and the recording was erased.

[0037]

As described in detail above, according to the present invention, with respect to the information recording medium utilizing the crystal-amorphous transition of the recording material, the information recorded with high sensitivity and high density can be read by a small system. In addition, it is possible to perform display without using a light source.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing temperature dependence of specific volume of a recording material.

Claims (1)

[Claims] 1. The recorded information is output by detecting the fluorescence intensity or electroluminescence intensity of an information recording medium for recording information by utilizing the crystal-amorphous transition of a recording material. Method for outputting information from an information recording medium.